1. Field of the Invention
The present invention relates to a technique for decomposing and removing organic contaminants contained in crop land soil, underground water, or the like. In particular, the present invention relates to a technique for decomposing and removing contaminants from soil, underground water, or the like, which has been contaminated by a plurality of organic contaminants, and to a technique for decomposing a persistent organic contaminant, by utilizing soil bacteria.
2. Description of the Related Art
In late years, a bio-remediation technique, which is able to decontaminate and safe the contaminated soil or the like by means of natural degrading abilities of microorganisms such as bacteria, has attracted attention as a technique for decomposing and removing persistent organic contaminants such as POPs in low concentration distributed widely in crop land soil, or the like. However, even though the conventional bio-remediation technique would utilize microorganisms such as bacteria effectively, the discovery of a degrading bacterium that decomposes an organic contaminant effectively has been difficult. Alternatively, even if the degrading bacterium can be discovered, the bacterium has its own living environment and the density of the degrading bacterium can be low in natural state, so a contaminant cannot be effectively prevented from remaining or scattering in the environment. In particular, in consideration of the application of the bio-remediation technique to contaminated soil or the like, problems have been risen such that the physical and chemical properties of contaminated soil affect the degrading bacteria and the degrading bacteria are extinct as a result of predation with protozoa in the contaminated soil. Therefore, even though there are increasing demands on the effective application of bio-remediation technique, in actual, such a technique has not been realized up to that required.
On the other hand, the inventors of the present invention have found that a porous material having a predetermined absorption constant or specific surface can be utilized as a degrading bacterial habitat for organic contaminants and have developed technique for accumulating and isolating a specific degrading bacterial species (Japanese Patent No. 3030370: Patent Document 1, Japanese Patent No. 2904432: Patent Document 2, and WO 00/078923: Patent Document 3). Those technologies have allowed any kind of organic contaminant which has been used in an agricultural chemical or the like and remained in environments, for example in soil, to be decomposed and removed by thickly accumulating and purifying degrading bacteria capable of decomposing the organic contaminant.
In many cases, two or more organic contaminants may cause environmental contamination such as soil and water contamination. However, there is no technique developed for simultaneously decomposing and removing those contaminants in place.
In addition, it is difficult to decompose organic contaminants which may be one of the causes of soil or water contamination, such as organochlorine pesticide PCNB (quintozene: pentachloronitrobenzene), which is hardly decomposed, and simazine (2-chloro-4,6-bis(ethylamino)-1,3,5-triazine), which has a long half-life and a low soil-adsorption coefficient. Therefore, novel technique for more effectively decomposing the organic contaminants has been demanded in the art.